Printing machines

ABSTRACT

A device for fixing a printing sleeve ( 3 ), in particular a printing form or a blanket drum, to a drive cylindrical shaft ( 1 ) on which a deformable cover ( 2 ) is arranged between the printing sleeve ( 3 ) and the shaft ( 1 ). The surface of the shaft ( 1 ) is grooved by a series of cavities ( 7 ) separated by bearing surfaces ( 12 ) which the cover ( 2 ) is rested on. The device also comprises an element for providing with the radial deformation of the deformable areas of the cover ( 2 ) by overpressure produced on the external face thereof or under-pressure on the internal face thereof. The device is characterized in that the shaft ( 1 ) and the printing sleeve ( 3 ) are provided with angular indexing elements ( 25 ).

The present invention relates to a printing machine and moreparticularly to a device intended to ensure fixation and positioning ofa removable printing sleeve on a support shaft of such a machine.

It is known that, in particular, the plate cylinders of the printingmachines are usually constituted by a cylindrical or conical shaft, onwhich is fixed a sleeve bearing, on its outer peripheral part, theengraving intended to make the print. It is also known that it isimportant, on such machines, that the user be in a position to replaceone sleeve by another, rapidly and easily.

It has therefore been proposed to ensure fixation of a printing sleeveon the cylindrical shaft by means of a hooping. To that end, there isexerted on the internal face of the sleeve a stress adapted to provokean expansion of the latter which then allows it to be fitted on theshaft. Once the fit is effected, it suffices to eliminate the stresswhich ensures the expansion of the sleeve for the latter then to bepressed strongly on the shaft.

Deformation of the sleeve is usually obtained by blowing pressurized airbetween the internal surface of the latter and the external surface ofthe shaft, through holes of small diameter provided in the latter.

Such deformation, of the order of some tenths of millimetre for metalsleeves, and of some millimetres for sleeves of composite materials, isobtained without difficulty when the sleeves present a small thickness.

It has also been proposed to ensure fixation of a sleeve on its shaft byprovoking a swelling of the latter after its positioning, under theeffect of a high hydraulic pressure (of the order of about 2.10⁷ Pa),and maintaining this pressure in the course of functioning. Such a modeof fixation makes it possible to obtain a perfect tightening of thesleeve on the shaft, as well as a very good concentricity of the sleevewith respect thereto in the course of use. However, the swelling of theshaft has for effect to provoke a deformation of the sleeve which, evenwhen it is slight, is detrimental to the good precision of the printingdevice. Moreover, in such a device, the necessity of maintaining, thehydraulic control pressure in the course of functioning, involves fromthe practical standpoint of implementation, employing particularlycomplex and therefore expensive devices.

Finally, it has been proposed in Patent EP-A-0855268, to ensure the holdof a sleeve of anilox on a cylindrical drive shaft by disposing betweenthe sleeve and the shaft a deformable cover and by hollowing out on theexternal surface of this shaft a series of cavities separated by holdingsurfaces on which the cover is in abutment, and rendering this coveradapted to be deformed so that it may present two positions, namely aposition of assembly in which each part of its surface, calleddeformable area, located opposite a cavity, is deformed in the latterunder the action of a stress, and a position of rest in which thedeformable area has resumed, at least in part, its initial shape, so asto be applied against the internal surface of the sleeve, this devicecomprising means adapted to ensure radial deformation of the deformableareas of the cover.

The present invention has for its object to propose means for angularlypositioning in precise manner the printing forms of a printing machineor a blanket cylinder when the latter is not continuous and comprises aninterruption.

The present invention thus has for its object a device for fixing aprinting sleeve, particularly a printing form or a blanket cylinder on acylindrical drive shaft in which a deformable cover is disposed betweenthe sleeve and the shaft, the surface of the shaft having a series ofcavities hollowed out therein, separated by bearing surfaces on whichthe cover is in abutment, the device comprising means adapted to ensureradial deformation of the deformable areas of the cover under the effectof an over-pressure on the external face of the latter or anunder-pressure on its internal face, characterized in that the shaft andthe sleeve are provided with angular indexing means.

These angular indexing means may be constituted by a finger disposed onone of the two pieces to be indexed and which is adapted to bepositioned in a cavity, of complementary shape, of the other piece. Thisfinger may be mounted to move in a housing and positioned in said cavityunder the action of elastic means, such as for example a compressionspring.

The sleeve will preferably be covered by a removable thin tube indexedwith respect thereto and the separation surface between the internalsurface of the tube and the external surface of the sleeve will be incommunication with means for controlled supply of pressurized air. Thisseparation surface may be connected by at least one conduit with thecontrolled supply of pressurized air of the separating surface existingbetween the sleeve and the cover.

In one embodiment of the invention, the downstream end of each conduitfor controlled supply of pressurized air of the separating surfaceexisting between the sleeve and the cover, will be provided with acontrol valve making it possible to send the flow of pressurized aireither towards this latter separation surface, when it is desired toremove the sleeve, or towards the separation surface of the sleeve andthe tube when it is desired to remove the latter.

The control valve will preferably be of the rotating type and theangular indexing means will be constituted by a finger fast with thisvalve so that this finger is in mesh with the sleeve when the valve ispositioned to send the flow of pressurized air in the direction of thetube.

Furthermore, the valve may comprise a finger adapted, in a givenposition, to block the axial displacement of the sleeve.

Various forms of embodiment of the present invention will be describedhereinafter by way of non-limiting example, with reference to theaccompanying drawings, in which:

FIG. 1 is a partial view in longitudinal cross section of a deviceaccording to the invention.

FIG. 2 is a partial side view of the device shown in FIG. 1.

FIG. 3 is a partial view in longitudinal cross section of a variantembodiment of the device according to the invention.

FIG. 3 a is an enlarged partial view of a closure valve that may be usedin the embodiment of the present invention shown in FIG. 3.

FIG. 3 b is a view in detail of a control member of a valve used in theembodiment of FIGS. 4 and 4 a.

FIG. 4 is a partial view in longitudinal cross section of anothervariant embodiment of the device according to the invention, the closurevalve being tipped in a first position.

FIG. 4 a is a partial view of the form of embodiment of the inventionshown in FIG. 4, the closure valve being tipped in a second position.

FIG. 1 shows an interchangeable printing cylinder according to theinvention which may equally well be, in the case of offset printing, aplate or blanket cylinder; in the case of a flexography printing, aplate cylinder; or in the case of photogravure, an engraved cylinder andpaper cylinder.

In FIG. 1, the device according to the invention is constituted by acylindrical shaft 1 of longitudinal axis xx′, which is intended tosupport and to drive a sleeve 3. The shaft 1 comprises, at each of itsends, headstocks 5, 5′ intended to ensure its hold and drive inrotation. The shaft 1 is hollowed out, on its periphery, with threeannular cavities 7 which are each in communication, by a radial conduit9, with a longitudinal channel 11 which opens out at one end of theshaft 1, the cavities 7 being separated by cylindrical, non-hollowedbearing surfaces 12. A cover 2 of small thickness is fitted on thebearing surfaces 12 of the shaft 1. This cover is made of glass-fibrereinforced epoxy resin.

The shaft 1 is hollowed out with a second axial, longitudinal channel 13which also opens out at one end of the shaft 1 and which is incommunication with five radial conduits 15 (of which only one has beenshown in the drawings).

In known manner, the cover 2 is pierced, opposite each conduit 15, withan orifice 18. On each side of this orifice, the shaft 1 is hollowed outwith two circular grooves in which O-rings 21 are disposed. AnotherO-ring 21′ is disposed in a circular groove at the other end of theshaft 1.

The sleeve 3 is constituted in particular by a metal, for example ofaluminium. It may equally well be constituted by synthetic materialsemploying a structure, particularly in honeycomb form, so as to presentconsiderable rigidity.

By injecting a flow of pressurized air A via the axial channel 13, sothat the flow traverses the cover 2 via the orifices 18, and creates,between the surface of the internal wall of the sleeve 3 and the surfaceof the external wall of the cover 2, a film of air under pressure, thoseparts of the cover 2 which are located opposite the cavities 7, arepushed inside the latter, which makes it possible easily to introducesaid sub-assembly inside the sleeve 3.

The shaft 1 is provided with a shoulder 20 against which the sleeve 3 isapplied. This shoulder is pierced with a cylindrical cavity of axis yy′parallel to axis xx′ of the shaft 1 and which opens to the outside via ahole of smaller diameter. The cavity receives a cylindrical finger 25and the hole receives the guiding shank 27 thereof. A compression spring29 urges the finger 25 towards the outside and the latter is retained inits cavity by holding means (of circlips type) provided on the guidingshank 27. Furthermore, the sleeve 3 is provided with a radial slot 31(possibly made by a milling cutter), whose width corresponds to thediameter of the finger 25, so that, in position of functioning, thelatter penetrates in said slot and thus ensures an angular indexation ofthe sleeve 3 with respect to the shaft 1.

The fact that the finger 25 is retractable inside the shoulder 20 makesit possible to avoid the deterioration of the sleeve 3 which mightoccur, at the end of stroke, in the event of the slot 31 not beinglocated opposite the finger 25, and this by reason of the mode ofdisplacement with very low friction (displacement on air cushion) of thesleeve 3.

The indexing finger 25 also presents another advantage. In effect, whenone changes format and passes to a sleeve of large diameter, it ispossible that the existing friction between the shaft 1 and the sleeve 3is not sufficient to transmit the torque necessary for deriving thesleeve in rotation, particularly in offset for the plate and blanketcylinders. In such a situation, the finger 25 then participates in thetransmission of a part of the torque, and it may be employed even whenno function of indexation proves necessary, as is the case when acontinuous blanket is employed.

In the present form of embodiment of the invention, the sleeve 3receives a plate 33 whose external face constitutes the active surfaceof the cylinder and which is fixed on the latter by embedding its twoends 33 a and 33 b in a longitudinal slot 35 hollowed out in the sleeve3, as shown in FIG. 2.

The external plate may, of course, be constituted differently and beformed for example of a fine tube 37 whose external surface constitutesthe active part. Assembling and dismantling of this tube 37 will beeffected by creating an overpressure of air between its internal surfaceand the external surface of the sleeve 3.

To that end, as shown in FIG. 3, use may be made of the same air supplyconduits and orifices 13 as those used for the dismantling/re-assemblyof the sleeve 3, and radial conduits 14 (of which only one is shown inthe drawings) conduct the pressurized air between the internal surfaceof the tube 37 and the external surface of the sleeve 3. In order toavoid the emergence of the sleeve 3 when it is desired to extract thetube 37, a removable retaining stop 39 has been provided, which preventsany slide of the sleeve on the shaft 1 during this operation.

This function of hold may also be performed by the indexing finger whichin that case will be disposed on the side opposite the shoulder 20 onthe side from which the sleeve 3 is extracted.

In such a form of embodiment of the invention, there will be provided,at the exit of each conduit 14 traversing the sleeve 3, a valve 16ensuring obturation of the latter when the tube 37 is not in place onthe sleeve 3.

As shown in FIG. 3 a, this valve may be constituted by a ball 42 whichis applied against a valve seat 43 by a compression spring 45. The valveseat 43 is such that, when the tube 37 is in place on the sleeve 3, theball 42 is pushed slightly by the latter so that a space is formedbetween the ball and the valve seat 43, thus leaving passage for thepressurized air, while, when the tube 37 is not in position on thesleeve 3, the spring 45 and the pressurized air push the ball 42 againstthe valve seat 43 and then obturates the latter.

As shown in FIGS. 3 b, 4, 4 a, in place of such a valve 16, it is also20 possible to use a valve 41 making it possible to direct the flow ofpressurized air coming from conduits 15 either between the sleeve 3 andthe cover 2 (dismantling/re-assembly of the sleeve 3), or between thetube 37 and the sleeve 3 (dismantling/re-assembly of the tube 37).

As shown in FIG. 3 b, the control member of this valve 41 may beconstituted by an element 47 in the form of a half-moon of which theposition of the rounded part 51 determines the immobilization or theaxial release of the sleeve 3. In this way, when, as shown in FIGS. 3 band 4, the rounded part 51 is in high position, it blocks the sleeve 3axially (this corresponding to a position of the valve 41 allowing theflow of pressurized air to be conducted between the tube 37 and thesleeve 3 so as to allow the withdrawal of the tube 37). On the contrary,as shown in FIG. 4 a, when the control of the valve 41 is in a positionsuch that its rounded part 51 is in low position, the latter no longerblocks the sleeve 3 (this corresponding to a position of the valve 41allowing the flow of pressurized air to be conducted between the cover 2and the sleeve 3), so as to allow the withdrawal of the latter.

1. Device for fixing a printing sleeve (3), particularly a printing formor a blanket cylinder on a cylindrical drive shaft (1) in which adeformable cover (2) is disposed between the sleeve (3) and the shaft(1), the surface of the shaft (1) having a series of cavities (7)hollowed out therein, separated by bearing surfaces (12) on which thecover (2) is in abutment, the device comprising means adapted to ensureradial deformation of the deformable areas of the cover (2) under theeffect of an over-pressure on the external face of the latter or anunder-pressure on its internal face, characterized in that the shaft (1)and the sleeve (3) are provided with angular indexing means (25). 2.Device according to claim 1, characterized in that the means adapted toensure radial deformation of the deformable areas of the cover (2) areconstituted by a controlled supply (13) of pressurized air of theseparating surface existing between the sleeve (3) and the cover (2). 3.Device according to claim 1, characterized in that the angular indexingmeans are constituted by a finger (25) disposed on one of the two pieces(1, 3) to be indexed, namely the shaft (1) or the sleeve (3), andadapted to be positioned in a housing (31), of complementary shape,provided in the other piece (3, 1).
 4. Device according to claim 3,characterized in that the finger (25) is mounted to move elastically ina cavity under the action of a spring (29).
 5. Device according to claim1, characterized in that the sleeve (3) is covered by a removable thintube (37) indexed with respect thereto.
 6. Device according to claim 5,characterized in that the separation surface between the internalsurface of the tube (37) and the external surface of the sleeve (3) isin communication with means for controlled supply of pressurized air. 7.Device according to claim 6, characterized in that said separationsurface is connected by at least one conduit (14, 15) with thecontrolled supply (13) of pressurized air of the separating surfaceexisting between the sleeve (3) and the cover (2).
 8. Device accordingto claim 7, characterized in that the conduit (14), connecting thecontrolled supply (13) of pressurized air of the separation surfaceexisting between the sleeve (3) and the shaft (1), comprises at itsdownstream end a closure valve (16) preventing the emergence of air whenthe sleeve (3) is not coated with a tube (37).
 9. Device according toclaim 7, characterized in that the downstream end of each conduit (15)for controlled supply of pressurized air of the separating surfaceexisting between the sleeve (3) and the cover (2), is provided with acontrol valve (41) making it possible to send the flow of pressurizedair either towards this latter separation surface, when it is desired toremove the sleeve (3), or towards the separation surface of the sleeve(3) and the tube (37) when it is desired to remove the latter. 10.Device according to claim 9, characterized in that the control valve(41) is of the rotating type and the angular indexing means areconstituted by a finger fast with this valve (41) so that this finger isin mesh with the sleeve (3) when the valve (41) is positioned to sendthe flow of pressurized air in the direction of the tube (37). 11.Device according to claim 9, characterized in that the valve (41)comprises a finger adapted, in a given position, to block the axialdisplacement of the sleeve (3).
 12. Device according to claim 2,characterized in that the angular indexing means are constituted by afinger (25) disposed on one of the two pieces (1, 3) to be indexed,namely the shaft (1) or the sleeve (3), and adapted to be positioned ina housing (31), of complementary shape, provided in the other piece (3,1).
 13. Device according to claim 12, characterized in that the finger(25) is mounted to move elastically in a cavity under the action of aspring (29).
 14. Device according to claim 10, characterized in that thevalve (41) comprises a finger adapted, in a given position, to block theaxial displacement of the sleeve (3).